Add a new varible to a method

[clark...@gmail.com]

I want to creat a new variable, for example, StreamWriter sw. I do like this:

            var stream_ref = new TypeReference("System.IO", "StreamWriter",MethodModule, null,true);

            var streamwriter = new VariableDefinition("writer", stream_ref);

            method.Body.Variables.Add(streamwriter);

and I get the NullReferenceException, I feel there lacks something, but I don't know where...I also wonder how to initialize the varible, like:

            StreamWriter sw = new StreamWriter("./test.txt", true);

and how to refer to it.

            Before, I try to create a varible like this:

            ins = ilProcessor.Create(OpCodes.Ldstr, @"./test.txt");

            ilProcessor.InsertBefore(instructions[0], ins);

            ins = ilProcessor.Create(OpCodes.Ldc_I4_1);

            ilProcessor.InsertBefore(method.Body.Instructions[1], ins);

            ins = ilProcessor.Create(OpCodes.Newobj, MethodModule.Import(typeof(System.IO.StreamWriter).GetConstructor( new Type[]{typeof(String), typeof(Boolean)})));

            ilProcessor.InsertBefore(instructions[2], ins);

            ins = ilProcessor.Create(OpCodes.Stloc_0);

            ilProcessor.InsertBefore(instructions[3], ins);

it doesn't work either.

I don't know why since the IL codes dumped from the one written in C# is like that, I know I miss something...

Another question is how to use the variable?

[Jb Evain]

Hi,

The first thing you need to do is to actually create a representation
of the variable, with a proper type:

var streamWriterTypeRef = Module.Import(typeof(System.IO.StreamWriter));
var streamWriteCtorRef =

Module.Import(typeof(System.IO.StreamWriter).GetConstructor( new
Type[]{typeof(String), typeof(Boolean)})));

var streamWriterVar = new VariableDefinition("writer", stream_ref);

method.Variables.Add(streamWriterVar);

Then you can use it by either using

il.Create(OpCodes.Stloc, streamWriterVar);
il.Create(OpCodes.Ldloc, streamWriterVar);

Or, you can use the Ldloc_N version where N is the index of
streamWriterVar in the Variables collection.

Jb

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[Jb Evain]

Cool !

I'm not exactly sure I understand what you mean.

Import (ImportReference in master), creates a reference scoped to your
module from a metadata element defined in another module. This is
conceptually different from a C# using.

Jb


On Wed, Mar 2, 2016 at 7:23 AM, <clark...@gmail.com> wrote:
> Thanks, it works! I wonder if the Import works like using.... in the C#
> code, but it works in minor scale, such as the type reference but not
> assembly reference?
>
> 在 2016年3月1日星期二 UTC+8下午7:20:19，clark...@gmail.com写道：

[clark...@gmail.com]

Thanks for your explantion, I am a green hand, so maybe I need more time the understand it. 

I clearly know Mono.cecil can do everything to a C# program, because it can read the original program and create new instructions to it. 

There is another question is: can it combines two programs into one or introduces some part of a program to another one?For example:

There is a program like:

Assembly A contains:

class program 1

{

     public main(){}

}

Assembly B contains:

class program 2

{

     variable a;

     public fun(){ a...}

}

I wonder how to introduce the fun() in program 2 to program 1. if this can be done, I can surely use 

Mono.cecil to let main() call the fun(). Now my initial idea is to create the variable and fun() in program 1, just 

the  same to program 2

but it feels a bit strange, is there a way to introduce them to program 1?

在 2016年3月3日星期四 UTC+8上午12:44:04，Jb Evain写道：

[Jb Evain]

It's possible, but it's not trivial.

IL-Repack does this: https://github.com/gluck/il-repack

Jb

[clark...@gmail.com]

Thank you very much! :) I will read it carefully.

在 2016年3月4日星期五 UTC+8上午12:47:56，Jb Evain写道：